Multicolor, multilayer photographic elements are well known in the art of color photography. Usually, these photographic elements have three different selectively sensitized silver halide emulsion layers coated on one side of a single support. The vehicle used for these emulsion layers is normally a hydrophilic colloid, such as gelatin. One emulsion layer is blue-sensitive, another green-sensitive and another red-sensitive. Although these layers can be arranged on a support in any order, they are most commonly arranged with the support coated in succession with the red-sensitive layer, the green-sensitive layer and the blue-sensitive layer (advantageously with a bleachable blue-light-absorbing filter layer between the blue-sensitive layer and the green-sensitive layer) or with the opposite arrangement and no filter layer. Colored photographic images are formed from latent images in the silver halide emulsion layers during color development by the coupling of oxidized aromatic primary amine color developing agent with couplers present either in the color developer solution or incorporated in the appropriate light-sensitive layers. Color photographic elements containing dye images usually utilize a phenolic or naphtholic coupler that forms a cyan dye in the red-sensitive emulsion layer, a pyrazolone or cyanoacetyl derivative coupler that forms a magenta dye in the green-sensitive emulsion layer and an acetylamide coupler that forms a yellow dye in the blue-sensitive emulsion layer. Diffusible couplers are used in color developer solutions. Non-diffusing couplers are incorporated in photographic emulsion layers. When the dye image formed is to be used in situ, couplers are selected which form non-diffusing dyes. For image transfer color processes, couplers are used which will produce diffusible dyes capable of being mordanted or fixed in the receiving sheet.
It is well known in the photographic art to utilize a stabilizing bath as the final step in the processing of both color films and color papers. Such baths can serve to reduce stain and/or enhance dye stability. A wide variety of different stabilizing compositions have been proposed for such use. Thus, the known stabilizing baths include those containing addition products of formaldehyde and a diazine or triazine as described in Mackey et al, U.S. Pat. No. 2,487,569 issued Nov. 8, 1949; aliphatic aldehydes as described in Harsh et al., U.S. Pat. No. 2,518,686 issued Aug. 15, 1950; addition products of formaldehyde and a urea, as described in Mackey, U.S. Pat. No. 2,579,435 issued Dec. 18, 1951; tetramethylol cyclic alcohols or ketones as described in Clarke et al., U.S. Pat. No. 2,983,607 issued May 9, 1961; glucoheptonates as described in Bard, U.S. Pat. No. 3,157,504 issued Nov. 17, 1964; amino acids as described in Jeffreys, U.S. Pat. No. 3,291,606 issued Dec. 13, 1966; mixtures of an aldehyde and an alkoxy-substituted polyoxyethylene compound as described in Seemann et al., U.S. Pat. No. 3,369,896 issued Feb. 20, 1968; compounds comprising a tri(hydroxymethyl)methyl group as described in Jeffreys et al., U.S. Pat. No. 3,473,929 issued Oct. 21, 1969; and addition complexes of an alkali metal bisulfate and an aldehyde as described in Mowrey, U.S. Pat. No. 3,676,136 issued July 11, 1972.
The formation of yellow stain in photographic color elements is believed to be related to the presence of unreacted coupler in emulsion layers and to be influenced by a number of factors such as heat, humidity, conditions to which the photographic element was subject in development, e.g., development time, temperature and replenishment rate, the contamination of developing composition, such as contamination by bleaching agents, and so forth. Dye stability is believed to also be affected by the presence of unreacted coupler in emulsion layers (since coupler and dye can react slowly with one another to degrade a color image) and to be influenced by such factors as temperature, humidity, ambient oxygen, and the spectral distribution and intensity of the light to which the dye image is subjected. Magenta dye stability is a particular problem, as the magenta dye image tends to fade much more rapidly than either the cyan dye image or the yellow dye image. Thus, the problems of stain formation and dye stability are interrelated and highly complex, and the stabilizing compositions known heretofore have typically been deficient in one or more respects as regards the overcoming of these problems.
Processes which are intended for rapid access processing of photographic color elements pose a particular difficulty with respect to the provision of an effective stabilizing bath. In order to shorten the total processing time, such processes typically do not have a wash step following the fixing or bleach-fixing step, and in consequence, the element passes directly from the fixing or bleaching-fixing bath into the stabilizing bath. This results in carryover of the fixing agent, which is usually a thiosulfate, into the stabilizing bath. The result of such carryover is decomposition of the thiosulfate and precipitation of elemental sulfur in the stabilizing bath with resultant fouling of both the processing apparatus and the photographic element. This problem is commonly referred to as "sulfurization" of the stabilizing bath.
A novel stabilizing bath that is highly effective in reducing yellow stain formation and increasing dye stability, and which eliminates or greatly reduces the tendency for sulfurization to occur, is described in the aforesaid U.S. patent application Ser. No. 064,633, filed June 22, 1987. This stabilizing bath is comprised of a dye stabilizing agent and a sufficient amount of an alkanolamine to effectively retard sulfurization. One problem in the use of such a bath however, is the tendency for the formation of precipitates to occur. These precipitates are typically a result of the presence of calcium ions. The source of the calcium can be the photographic emulsion layers of the photographic element undergoing processing or the use of hard water in the formation or replenishment of the processing solutions. Such formation of precipitates is highly undesirable, as it can lead to the formation of sludge in the processing solutions, scum on the photographic elements that are processed therein, and scale on the equipment used in processing.
In an attempt to avoid the problem of calcium precipitates, it has long been the practice in the photographic art to complex the calcium in an un-ionized form by the use of a sequestering agent. Among the sequestering agents which have been proposed for this purpose are polyphosphates, polycarboxylic acids, hydroxy acids such as gluconic acid, oxyacetic acids such as diglycolic acid, pyridine carboxylic acids, and organophosphonates. However, there are many problems associated with the use of these sequestering agents. Examples of such problems include insufficient sequestering power, a tendency to undergo hydrolysis in the processing solution, a tendency to catalyze the decomposition of some processing agents, and a tendency to undergo reactions leading to the formation of insoluble compounds. Patents relating to the use of sequestering agents in photographic processing compositions include U.S. Pat Nos. 2,172,216, 2,541,470, 2,656,273, 2,875,049, 3,201,246, 3,462,269, 3,746,544, 3,839,045, 3,994,730, 4,083,723, 4,142,895 and 4,264,716 and British Pat. Nos. 712,356, 795,914, 1,251,462, 1,495,504 and 1,496,326.
Of particular importance among the classes of sequestering agents which are used commercially in both color and black-and-white processing compositions--for the purpose of preventing, or at least reducing, the precipitation of calcium salts--are the aminopolycarboxylic acids and the aminopolyphosphonic acids. In some instances, only a single sequestering agent is employed, but it is also well known to use mixtures of two or more sequestering agents, including mixtures of two or more different members of the class of aminopolycarboxylic acids, mixtures of two or more different members of the class of aminopolyphosphonic acids, and mixtures of at least one aminopolycarboxylic acid with at least one aminopolyphosphonic acid.
In a stabilizing bath of the type containing a dye stabilizing agent and an alkanolamine, as described in the aforesaid U.S. patent application Ser. No. 064,633 filed June 22, 1987, it is a particularly difficult problem to reduce or eliminate the formation of unwanted precipitates. This stabilizing bath is used as the final bath in the process and is not washed from the photographic element. Thus, the components of the stabilizing bath remain in the element during the drying step and must be able to withstand the elevated temperatures used in drying. When subjected to such conditions, sequestering agents of either the aminopolycarboxylic acid type or the aminopolyphosphonic acid type tend to degrade and may gradually bring about the formation of yellow stain during storage, with a resulting increase in D.sub.min that is highly undesirable. Thus, while they alleviate the problem of precipitates of calcium they cause a staining problem that renders their use impractical.
It is toward the objective of providing a novel stabilizing bath that increases dye stability, avoids precipitate formation, reduces the tendency for sulfurization to occur, and does not cause staining that the present invention is directed.